SDS Bonding question

[Smart $]

I understood you where not talking about a utility transformer.

But the NEC treats any SDS the same way just because the transformer is in the building doesn't mean you don't have to hook it to the earth grounding electrode on that buildings electrical system.

And even if the primary and secondary grounded conductors are bonded as the NESC requires doesn't mean it is not a SDS.

The hypothetical transformer under discussion does not fall under NESC compliance. Please do not confuse the discussion with NESC requirements.

Regarding NEC compliance, a primary-side solidly grounded circuit conductor connected or otherwise bonded to the X0 terminal of the hypothetical transformer or its secondary grounded conductor removes the transformer from being classified as a separately derived system. Therefore, it is not bound to the requirements for a separately derived system.

The only question that remains, which has yet to be shown by NEC standards, is if such connection is non-compliant. Can you reference an NEC requirement which establishes said connection as non-compliant?

 

[crossman]

Smart, I haven't forgotten this thread. I will have some time tomorrow to dig around in the NEC and see if I can come up with something that would say we can't do it. But right now, I can't remember anywhere that it says you can't.

 

[RB1]

Connecting the grounded circuit conductor from the primary feeder to the transformer case would be a violation of 250.142(B). I don't know of a method where you could provide the equipment grounding for the transformer required by 250.110 and not violate 250.142(B).

 

[ronaldrc]

The hypothetical transformer under discussion does not fall under NESC compliance. Please do not confuse the discussion with NESC requirements.

Regarding NEC compliance, a primary-side solidly grounded circuit conductor connected or otherwise bonded to the X0 terminal of the hypothetical transformer or its secondary grounded conductor removes the transformer from being classified as a separately derived system. Therefore, it is not bound to the requirements for a separately derived system.

The only question that remains, which has yet to be shown by NEC standards, is if such connection is non-compliant. Can you reference an NEC requirement which establishes said connection as non-compliant?

Please, I think they know where the NESC stops and the NEC takes over.

But to comply to NEC the transformers secondary or XO needs to hook back to the buildings grounding electrode.

It doesn't necessarily have to be a conductor it could be a metal water supply line Etc.

Regarding NEC compliance, a primary-side solidly grounded circuit conductor connected or otherwise bonded to the X0 terminal of the hypothetical transformer or its secondary grounded conductor removes the transformer from being classified as a separately derived system. Therefore, it is not bound to the requirements for a separately derived system.?

Am I understanding you to say this secondary is going to float and not have a earth ground?